1. Field of the Invention
This invention relates generally to cementitious compositions. More specifically, this invention relates to Portland cement compositions particularly suitable for use as pointing compounds, more commonly known as tile grout.
2. Description of the Prior Art
In the setting of ceramic tile, it is now an established practice to fill the areas or joints between the adjacent tiles with a bonding material. The material used to fill the joints is referred to as pointing compound or, as it is more commonly known, tile grout. A variety of tile grout compounds presently exist, e.g., acrylic grout, epoxy grout and Portland cement base grout.
All tile grouts, regardless of the type, are required to provide certain properties. These properties include workability, stain resistance and easy cleanup. Workability is required to facilitate the spreading of the grout completely into the joints beteen the adjacent tile edges without creating any vacant areas. Workability is particularly significant in dry set Portland cement tile grouts because the composition is typically packaged as a dry powder that must be mixed with water to a workable consistency at the job site.
The property of stain resistance is important because ceramic tile is used both functionally and decoratively. Thus, permanent stains on either the ceramic tile or the grout will mar and detract from the decorative appearance of the installation. The face of the ceramic tile is essentially impervious and, therefore, free from permanent staining. The grout must be made both as resistant to stain and capable of withstanding scouring as possible.
Easy cleanup is another important property of grout due to the nature of the way in which tile grout is installed. Tile grout must be installed after the ceramic tile is firmly set. Thus, when troweled into the joints between the ceramic tile edges, some of the excess grout will adhere to the tile face. The grout must be removed from the tile face without disturbing the grout in the joints.
A property particular to Portland cement dry set grout is the capacity to retain water after troweling. Water retention is desirable in Portland cement grouts because the ceramic tile bisque and the substrate on which the tile is set tend to absorb water from the grout. Portland cement requires water to properly set; thus, removal of water from a Portland cement grout prevents the grout from properly curing.
At present, dry set Portland cement grout is a grout commonly used to fill the joints between the coarse edges of ceramic tile that has been dry set. A dry set Portland cement grout normally is made up of Portland cement, a filler such as fine limestone or marble dust, and a cellulose ether such as methyl cellulose or hydroxyethyl cellulose. Illustrative of dry set Portland cement grouts are the grouts disclosed in U.S. Pat. No. 2,820,713 (Wagner, issued Jan. 21, 1958) and U.S. Pat. No. 2,838,411 (Wagner, issued June 10, 1958). More recently, an improved dry set grout has been developed at Tile Council of America, Princeton, N.J., in which a long chain organic polymer is used as an ingredient. The specific detail of both the grout and mortar compositions having a long chain organic polymer as an ingredient are disclosed in U.S. Pat. Nos. 4,021,257 (Bernett, May 3, 1977) and 4,043,827 (Bernett, Aug. 23, 1977). Therein, the dry set grouting composition is disclosed as a composition comprised of 75% to 100% Portland cement, 0% to 25% filler, such as limestone, 0.1% to 0.6% of a cellulose ether and 0.001% to 0.2% of a long chain organic polymer. Illustrative long chain organic polymers are hydroxyalkyl starch and polyacrylamide.